In the chemical industry, it is sometimes necessary to use or store particularly acidic reagents or products or corrosives that make it impossible to use traditional containers or tanks whose steel walls would be attacked and destroyed.
A solution consists in using in this case a reactor tank or container or other containers whose internal wall is glass-lined. This inert and very resistant coating ensures protection of the tank or container against the aggressive attack of the contained material.
However, in order to avoid any risk of deterioration of the container and any risk of leakage that would be dangerous for people, the material, the environment, and the integrity of this glass-lined protective coating must be ensured at all times.
The integrity of this glass-lined protective coating depends closely on the internal geometry of the container and its interior elements. Thus, angular zones, which are very difficult to enamel, must be avoided. On the contrary, smooth and curved surfaces are preferred.
A sudden variation in temperature, either on the glass-lined or steel side can lead to the destruction of the glass-lined coating by thermal shock. The most dangerous thermal shocks are caused by projections of cold materials onto a hot glass-lined surface.
Moreover, during the process of glass-lining, treated surfaces generally undergo heat treatment requiring heating to a temperature of 700 to 850° C., which induces significant thermal expansion. Such thermal expansion causes tension which in turn can damage or deteriorate the protective glass-lining.
In addition, it is often necessary in the chemical industry to agitate the material in the container. This agitation is generally carried out by means of an agitator and it can be associated with one or more baffles.
Conventionally, the tanks or containers equipped with an impeller, which is inserted through a nozzle in the tank or container, comprise one or more baffles. More rarely, the baffles can be secured over their entire length on the internal surface of the tank or container.
A baffle is a device that allows better agitation, in particular by creating additional turbulence in the agitated medium and by preventing the formation of a swirl or vortex.
In the case of devices welded inside the tank or container to be glass-lined, the extent of the stresses is increased due to thermal expansion if these devices are welded along a critical length or along their entire periphery against the internal wall of the tank or container.